Hydrogen generating apparatus

ABSTRACT

A hydrogen generating apparatus includes a chemical reaction chamber, a chemical solution reservoir, and an unpowered pressure producing member for moving a chemical solution from the chemical solution reservoir to the chemical reaction chamber.

FIELD OF THE INVENTION

This invention relates to fuel cells. More particularly, this inventionrelates a method and apparatus for hydrogen generation for a fuel cell.

BACKGROUND OF THE INVENTION

Over the past century the demand for energy has grown exponentially.With the growing demand for energy, many different energy sources havebeen explored and developed. One of the primary sources for energy hasbeen and continues to be the combustion of hydrocarbons. However, thecombustion of hydrocarbons usually results in incomplete combustion andnon-combustibles that contribute to smog and other pollutants in varyingamounts.

As a result of the pollutants created by the combustion of hydrocarbons,the desire for cleaner energy sources has increased in more recentyears. With the increased interest in cleaner energy sources, fuel cellshave become more popular and more sophisticated. Research anddevelopment on fuel cells has continued to the point where manyspeculate that fuel cells will soon compete with the gas turbinegenerating large amounts of electricity for cities, the internalcombustion engine powering automobiles, and batteries that run a varietyof small and large electronics.

Fuel cells conduct an electrochemical energy conversion of hydrogen andoxygen into electricity and heat. Fuel cells are similar to batteries,but they can be “recharged” while providing power.

Fuel cells provide a DC (direct current) voltage that may be used topower motors, lights, or any number of electrical appliances. There areseveral different types of fuel cells, each using a different chemistry.Fuel cells are usually classified by the type of electrolyte used. Thefuel cell types are generally categorized into one of five groups:proton exchange membrane (PEM) fuel cells, alkaline fuel cells (AFC),phosphoric-acid fuel cells (PAFC), solid oxide fuel cells (SOFC), andmolten carbonate fuel cells (MCFC).

PEM Fuel Cells

The PEM fuel cells are currently believed to be the most promising fuelcell technology, and use one of the simplest reactions of any fuel cell.Referring to FIG. 1, a PEM fuel cell will typically include four basicelements: an anode (20), a cathode (22), an electrolyte (PEM) (24), anda catalyst (26) arranged on each side of the electrolyte (24).

The anode (20) is the negative post of the fuel cell and conductselectrons that are freed from hydrogen molecules such that the electronscan be used in an external circuit (21). The anode (20) includeschannels (28) etched therein to disperse the hydrogen gas as evenly aspossible over the surface of the catalyst (26).

The cathode (22) is the positive post of the fuel cell, and has channels(30) etched therein to evenly distribute oxygen (usually air) to thesurface of the catalyst (26). The cathode (22) also conducts theelectrons back from the external circuit to the catalyst, where they canrecombine with the hydrogen ions and oxygen to form water. Water is theonly by-product of the PEM fuel cell.

The electrolyte (24) is the proton exchange membrane (PEM) (24). The PEMis a specially treated porous material that conducts only positivelycharged ions. The PEM (24) prevents the passage of electrons.

The catalyst (26) is typically a platinum powder thinly coated ontocarbon paper or cloth. The catalyst (26) is usually rough and porous soas to maximize the surface area of the platinum that can be exposed tothe hydrogen or oxygen. The catalyst (26) facilitates the reaction ofoxygen and hydrogen.

In a working fuel cell, the PEM (24) is sandwiched between the anode(20) and the cathode (22). The operation of the fuel cell can bedescribed generally as follows. Pressurized hydrogen gas (H₂) enters thefuel cell on the anode (20) side. When an H₂ molecule comes into contactwith the platinum on the catalyst (26), it splits into two H⁺ ions andtwo electrons (e⁻). The electrons are conducted through the anode (20),where they make their way through the external circuit (21) that may beproviding power to do useful work (such as turning a motor or lighting abulb (23)) and return to the cathode side of the fuel cell.

Meanwhile, on the cathode (22) side of the fuel cell, oxygen gas (O₂) isbeing forced through the catalyst (26). In some PEM fuel cell systemsthe O₂ source may be air. As O₂ is forced through the catalyst (26), itforms two oxygen atoms, each having a strong negative charge. Thisnegative charge attracts the two H⁺ ions through the PEM (24), wherethey combine with an oxygen atom and two of the electrons from theexternal circuit to form a water molecule (H₂O).

The PEM fuel cell reaction just described produces only about 0.7 volts,therefore, to raise the voltage to a more useful level, many separatefuel cells are often combined to form a fuel cell stack.

PEM fuel cells typically operate at fairly low temperatures (about 80°C./176° F.), which allows them to warm up quickly and to be housed ininexpensive containment structures because they do not need any specialmaterials capable of withstanding the high temperatures normallyassociated with electricity production.

Hydrogen Generation for Fuel Cells

As discussed above, each of the fuel cells described uses oxygen andhydrogen to produce electricity. The oxygen required for a fuel cell isusually supplied by the air. In fact, for the PEM fuel cell, ordinaryair at ambient conditions is pumped into the cathode. However, hydrogenis not as readily available as oxygen.

Hydrogen is difficult to generate, store and distribute. One commonmethod for producing hydrogen for fuel cells is the use of a reformer. Areformer uses hydrocarbons or alcohol fuels to produce hydrogen, whichis then fed to the fuel cell. Unfortunately, reformers are problematic.If the hydrocarbon fuel is gasoline or some of the other commonhydrocarbons, SO_(x), NO_(x) and other undesirable products are created.Sulfur, in particular, must be removed or it can damage the electrodecatalyst. Reformers usually operate at high temperatures as well, whichconsumes much of the energy of the feedstock material.

Hydrogen may also be created by low temperature chemical reactionsutilizing a fuel source in the presence of a catalyst. However, manyproblems are associated with low temperature chemical reactions forproducing hydrogen. One of the primary problems is the requirement forpumps to move the chemical mixture into a reaction chamber filled with acatalytic agent. The use of a pump consumes at least some of the powerthat the fuel cell is generating (called parasitic power). If the powerconsumed by the pump becomes too high, the operation of the fuel cell toproduce electricity becomes uneconomical.

Further, the chemical mixture provided to the reaction chamber must beaccurately metered to facilitate a chemical reaction that willefficiently generate electric power. Accurate metering equipment addsexpense, complexity, and sensitivity to the pumping system and increasesthe parasitic power consumption. Typical fuel cells are also usuallyorientation-specific, meaning that metering of the chemical mixture canonly be done when the fuel cell is in certain orientations.Orientation-specific fuel cell systems limit their usefulness forportable consumer electronics and other devices that may be used inmultiple and changing orientations.

In addition, another challenge to using fuel cells in portable consumerproducts such as digital cameras and laptop computers is providing ahydrogen fuel source that is safe and energy-dense. While there havebeen fuel cell systems used to generate electricity, such as the PEMfuel cell described above, they are typically not small or dense enoughto be used in most portable consumer products.

SUMMARY OF THE INVENTION

The present invention provides, among other things, a hydrogengenerating apparatus including a chemical reaction chamber, a chemicalsolution reservoir, and an unpowered pressure producing member formoving a chemical solution from the chemical solution reservoir to thechemical reaction chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the invention willbecome further apparent upon reading the following detailed descriptionand upon reference to the drawings in which:

FIG. 1 is an unassembled perspective view of a PEM fuel cell apparatus.

FIG. 2 is an overview diagram of a fuel cell apparatus according to oneembodiment of the present invention.

FIG. 3 is a diagrammatical view of hydrogen generator according to oneembodiment of the present invention.

FIG. 4A is a diagrammatical view of a hydrogen generator according toanother embodiment of the present invention.

FIG. 4B is a perspective view of a hydrogen generator implementationaccording to the embodiment of FIG. 4A.

FIG. 4C is a perspective view of some of the internal components of thehydrogen generator implementation according to the embodiment of FIG.4B.

FIG. 5 is a diagrammatical view of a hydrogen generator according toanother embodiment of the present invention.

FIG. 6 is a diagrammatical view of a hydrogen generator according toanother embodiment of the present invention.

FIG. 7 is a diagrammatical view of a hydrogen generator according toanother embodiment of the present invention.

FIG. 8 is a diagrammatical view of a hydrogen generator according toanother embodiment of the present invention.

FIG. 9 is a conceptual diagram of a control structure for a hydrogengenerator according to an embodiment of the present invention.

FIG. 10 is a flow diagram for a control algorithm for a hydrogengenerator according to an embodiment of the present invention.

In the drawings, identical reference numbers indicate similar, but notnecessarily identical, elements. While the invention is susceptible tovarious modifications and alternative forms, specific embodimentsthereof have been shown by way of example in the drawings and are hereindescribed in detail. It should be understood, however, that thedescription herein of specific embodiments is not intended to limit theinvention to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Illustrative embodiments of the invention are described below. As willbe appreciated by those skilled in the art, the present invention can beimplemented in a wide variety of chemical reactions especially those forproducing hydrogen for fuel cells. The fuel cell applications include,but are not limited to, PEM fuel cells, AFCs, PAFCs, SOFCs, and MCFCs.

Turning now to the figures, and in particular to FIG. 2, an overview ofa fuel cell system according to one embodiment of the present inventionis shown. According to the embodiment of FIG. 2, there is a fuel cell(40) in fluid communication with a hydrogen generating apparatus (42).The hydrogen generating apparatus (42) may provide a supply of hydrogengas along the path represented by an arrow (44). A supply of oxygen,that may be provided by ambient air, may also be in fluid communicationwith the fuel cell (40) as represented by another arrow (46).

The fuel cell (40) may provide power via an external circuit (48) to anelectrical load (50). An electrical load may encompass any electricallyoperated device including, but not limited to, a digital camera, alaptop computer, and other portable electronics. The external circuit(48) may also be connected to an optional electrical capacitor orbattery (52) which is shown in electrical parallel with the fuel cell(40) for providing auxiliary power to the electrical load (50).

The hydrogen generating apparatus (42) is necessary for providinghydrogen gas to the fuel cell (40) so as to drive an energy-producingchemical reaction within the fuel cell (40). The hydrogen generatingapparatus (42) may take many different forms. Referring to FIG. 3, onepossible embodiment of a hydrogen generating apparatus (54) according tothe present invention is shown. According to the embodiment of FIG. 3,the hydrogen generating apparatus (54) includes a chemical solutionreservoir, shown in the present embodiment as a fresh solution bag (56)containing a supply of hydrogen-bearing fuel. The hydrogen-bearing fuelmay include, but is not limited to, an aqueous metal hydride such assodium borohydride, and an amine borane, each of which produce hydrogengas. The fresh solution bag (56) is preferably a flexible bag made ofplastics, elastomers, or other materials that are generally deformableand capable of containing fluid solutions.

Arranged about the fresh solution bag (56) may be an unpowered pressureproducing member, for example a spring (58) located adjacent to thefresh solution bag (56). The term “unpowered” signifies that thepressure producing member does not consume electrical energy to operate,nor does it require power from a motor. The spring (58) may include oneor more members biased toward the fresh solution bag (56) to increasethe pressure of the hydrogen-bearing fuel contained inside the freshsolution bag (56). The pressurization of the hydrogen-bearing fuelfacilitates movement of the hydrogen-bearing fuel from the freshsolution bag (56) to a chemical reaction chamber (60). The spring (58)and fresh solution bag (56) may constitute a “spring-bag,” i.e., aflexible bag or container for containing a chemical solution on whichpressure is exerted by a mechanical pressure producing member, forexample, a spring or other biasing member, to help expel the chemicalsolution.

The chemical reaction chamber (60) may be separate from the freshsolution bag (56) and designed to house a chemical reaction thatproduces hydrogen gas. The chemical reaction chamber (60) may include awide variety of materials according to the reactants used to produce thehydrogen gas. The chemical reaction chamber (60) may be flexible orrigid, although in the present embodiment the chemical reaction chamber(60) is rigid. In addition, the chemical reaction chamber (60) maycontain a catalyst (62) for increasing the reaction rate of thehydrogen-bearing fuel. The catalyst (62) may include, but is not limitedto, a noble metal catalyst such as ruthenium, rhodium, or platinum. Thecatalyst (62) may include other metals such as nickel.

The movement of the hydrogen-bearing fuel from the fresh solution bag(56) to the chemical reaction chamber (60) may be facilitated by a fluidpath such as a tubing (64). In addition, the flow of thehydrogen-bearing fuel from the fresh solution bag (56) to the chemicalreaction chamber (60) may be controlled by a valve, such as amicro-valve (66). The micro-valve (66) may be arranged at any convenientlocation along the tubing (64) for controlling the flow from the freshsolution bag (56). The micro-valve (66) is available from a variety ofcommercial sources and may be controlled in at least three primary ways.The micro-valve (66) may be controlled by the time between pulses(micro-valve (66) pulsing frequency), the pulse width (duration themicro-valve (66) is held open), and/or variation in aperture size.Variable aperture size control indicates analog control of how far openor closed the micro-valve is. The micro-valve (66) may thus enableprecise control of the flow of the hydrogen-bearing fuel into thechemical reaction chamber (60). The micro-valve (66) may be normallyclosed. Therefore, when hydrogen gas is needed, the micro-valve (66) isopened to allow the hydrogen-bearing fuel, pressurized by the spring(58), to flow into the reaction chamber (60). An optional check valve(68) may also be included. In the embodiment shown, the check valve (68)is located downstream of the micro-valve (66), but this is notnecessarily so. Check valve (68) may be inserted at any point along thetubing (64). Check valve (68) is commercially available from a number ofdifferent sources and is a one-way valve. Thus, check valve (68)prevents the backflow of products or of the hydrogen-bearing fuel in theevent of a pressure build up in the chemical reaction chamber (60).

Operation of the hydrogen generating apparatus (54) may be described asfollows. A hydrogen-bearing fuel source such as sodium borohydride isinserted into the fresh solution bag (56). In some embodiments, thefresh solution bag (56) may be inserted separately against the spring(58) after being filled. Alternatively, the fresh solution bag (56) maybe filled while in the arrangement shown in FIG. 3. The spring (58) isarranged adjacent to and biased toward the fresh solution bag (56) andtherefore pressurizes the sodium borohydride contained by the freshsolution bag (56). When hydrogen gas is needed by a fuel cell to providean electrical current, the micro-valve (66) may be opened or oscillatedto allow pressurized sodium borohydride to move from the fresh solutionbag (56) to the chemical reaction chamber (60). When the sodiumborohydride enters the chemical reaction chamber (60) and encounters thecatalyst (62), hydrogen gas is released from the sodium borohydridesolution. The hydrogen gas released from the sodium borohydride solutionmay then be supplied to a fuel cell such as the fuel cell apparatus ofFIGS. 1 and 2.

Prior hydrogen generating apparatus require pumps of one kind or anotherto move the supply of hydrogen-bearing fuel from a reservoir to areaction chamber. As indicated as above, pumps add significantly to theparasitic losses of a fuel cell apparatus and occupy space, limiting theenergy density available for the fuel cell apparatus. Advantageously,the present invention decreases parasitic loss and reduces spacerequirements by providing a mechanical pressure source to facilitatemovement of the hydrogen-bearing fuel from a reservoir to a reactionchamber.

Referring next to FIG. 4A, another embodiment of a hydrogen generatingapparatus (154) according to the present invention is shown. Similar tothe embodiment of FIG. 3, the hydrogen generating apparatus (154) ofFIG. 4A may include a chemical solution reservoir such as a freshsolution bag (156) and a chemical reaction chamber (160). However,according to the embodiment of FIG. 4A, the fresh solution bag (156) maybe entirely contained by the chemical reaction chamber (160). Oneadvantage of such an arrangement is the conservation of space and anincreased energy density. The fresh solution bag (156) is generallyflexible and therefore as the supply of hydrogen-bearing fuel (and thevolume of the fresh solution bag (156)) decreases, the portion (161) ofthe chemical reaction chamber (160) dedicated to conducting the chemicalreaction increases. The chemical reaction chamber (160), as opposed tothe fresh solution bag (156), may be a rigid structure and may contain acatalyst. The arrangement of FIG. 4A is a space-efficient configurationthat eliminates any duplicate volume.

In addition to being space-efficient, the configuration of FIG. 4Aincludes an arrangement of the fresh solution bag (156) within thechemical reaction chamber (160) such that fresh solution bag (156) isexposed to the pressure of the chemical reaction chamber (160).Therefore, as the chemical reaction chamber (160) pressurizes duringoperation, the pressure transfers to the fresh solution bag (156) and avery low-force pressure producing member may be used to initiate flowfrom the fresh solution bag (156) to the chemical reaction chamber (160)at any chemical reaction chamber (160) pressure. Accordingly, becausethe fresh solution bag (156) is always exposed to the chemical reactionchamber (160) pressure, the low-force pressurizing member may below-force and light-weight. In the present embodiment the low-forcepressurizing member is a light-weight coiled spring (158). Further, thechemical reaction chamber (160) which contains the fresh solution bag(156) may be light-weight and smaller than a conventional reactorbecause it does not need to be large and stiff enough to handle highforce (and therefore a larger) spring.

The coiled spring (158) of the present embodiment is disposed inside thechemical reaction chamber (160) between a wall (163) of the chemicalreaction chamber (160) and the fresh solution bag (156) or a memberabutting the solution bag (156). Accordingly, the coiled spring (158)applies a force to the fresh solution bag (156) and increases thepressure on the fluid contained in the fresh solution bag (156) enoughto move fluid from the fresh solution bag into the chemical reactionchamber (160). The combination of a flexible bag and a springconstitutes a spring-bag, as defined herein.

A fluid communication path (164) provides a path for the solution orfuel from the bag (156) to enter the reaction chamber (160). Accordingto the embodiment shown in FIG. 4A, the fluid communication path (164)is external to the reaction chamber (160) and runs between the freshsolution bag (156) and that portion (161) of the chemical reactionchamber (160) dedicated to conducting the chemical reaction, but this isnot necessarily so. The fluid communication path (164) may also becontained entirely within the chemical reaction chamber (160). As withthe embodiment shown in FIG. 3, the fluid communication path (164)includes a valve such as a micro-valve (166) to meter fluid flow fromthe fresh solution bag (156) to the portion (161) of the chemicalreaction chamber (160) dedicated to conducting the chemical reaction.

Operation of the hydrogen generating apparatus (154) shown in FIG. 4Amay be described as follows. A hydrogen-bearing fuel source such assodium borohydride is inserted into the fresh solution bag (156). Thefilled fresh solution bag (156) may be inserted separately against thecoiled spring (158) in some embodiments, or the fresh solution bag (156)may be filled while in the arrangement shown in FIG. 4A. When the freshsolution bag (156) is filled with an aqueous solution of sodiumborohydride or other fuel, it occupies a significant portion of thevolume defined by the chemical reaction chamber (160). The coiled spring(158) is arranged adjacent to, and is compressed against, the freshsolution bag (156). Therefore, the coiled spring (158) pressurizes thesodium borohydride contained by the fresh solution bag (156). Thepotential energy stored in the coiled spring (158) (when compressed)provides chemical solution-moving power without adding to parasiticlosses in the way that pumps of prior hydrogen-generating systems do.

When hydrogen gas is needed by a fuel cell to provide an electricalcurrent, the micro-valve (166) may be opened or oscillated to allowpressurized sodium borohydride to move from the fresh solution bag (156)to the portion (161) of the chemical reaction chamber (160) availablefor chemical reaction. When the sodium borohydride enters the portion(161) of the chemical reaction chamber (160) available for chemicalreaction and encounters a catalyst (not shown), hydrogen gas is releasedfrom the aqueous sodium borohydride solution. The hydrogen gas releasedfrom the aqueous sodium borohydride solution may then be supplied to afuel cell such as the fuel cell apparatus shown in FIGS. 1 and 2. As thesupply of aqueous sodium borohydride solution is consumed, the freshsolution bag (156), which is flexible, reduces in volume and providesmore volume within the chemical reaction chamber (160) for conductingthe chemical reaction.

Referring next to FIG. 4B, an actual implementation according to theembodiment of FIG. 4A is shown. According to the embodiment of FIG. 4B,the hydrogen generating apparatus (154) includes a frame (159) and awindow (161) (which is shown with a cut-away portion (165)) form thechemical reaction chamber (160). A baffled pressure plate (167) isdisposed within the reaction chamber (160) and the spring (158) isarranged between the window (161) and the baffled pressure plate (167).The fresh solution bag (156) is disposed opposite of the spring (158)and adjacent to the baffled pressure plate (167). The fluidcommunication path (164) extends from the fresh solution bag (156) andis contained in the present embodiment entirely within the chemicalreaction chamber (160). The fluid communication path (164) andassociated components can be more clearly seen with reference to FIG.4C. The micro-valve (166) is arranged along the fluid communication path(164) with an outlet orifice (171), which allows fluids that travelthrough the micro-valve (166) to enter into the chemical reactionchamber (160) in a controlled manner.

Referring next to FIG. 5, another embodiment of a hydrogen generatingapparatus (254) according to the present invention is shown. Similar tothe embodiment of FIG. 4, the embodiment of FIG. 5 includes a chemicalsolution reservoir shown as a flexible fresh solution bag (256),contained within a chemical reaction chamber (260). The flexible freshsolution bag (256) may also be considered a spring-bag as definedherein. According to the embodiment of FIG. 5, the pressure producingmember is the spring-bag (256) itself. The flexible bag (256) ispreferably made of elastomers such as rubber or other materials thatprovide a bias or mechanical spring-like force toward a particular shapeor volume. Thus, the material exerts a pressure on any fluid containedtherein when expanded under pressure to contain that fluid against thenatural bias for a smaller shape or volume. Therefore, the spring-bag(256) may operate similarly or identically to the embodiment of FIG. 4,however, the coiled spring (158, FIG. 4) is not necessary for theembodiment of FIG. 5. Instead of a coiled spring, the spring-bag (256)is provided with a chemical solution such as aqueous sodium borohydridesuch that the spring-bag (256) is expanded. Normally, the expansion willbe within the elastic limits of the spring-bag (256). The expansion ofthe spring-bag (256) provides a pressurizing force on the chemicalsolution contained by the spring-bag (256) in much the same way aballoon may hold a volume of air under pressure.

A fluid communication path (264) facilitates the transfer of thechemical solution (such as aqueous sodium borohydride) from thespring-bag (256) to the reaction occurring in the chemical reactionchamber (260). The fluid communication path (264) may be at leastpartially external to the chemical reaction chamber (260), as shown, orthe fluid communication path (264) may be internal to the chemicalreaction chamber (260). The chemical reaction chamber (260) may beflexible or rigid, and may also contain a catalyst for increasing therate of reaction of the chemical solution. The fluid communication path(264) may also include a control valve such as micro-valve (266) tometer the chemical solution from the spring-bag (256) to the reactionwithin the chemical reaction chamber (260). Similar to the embodimentshown in FIG. 4, as the supply of aqueous sodium borohydride istransferred from the spring-bag (256) to the chemical reaction chamber(260), the volume of the spring-bag (256) decreases. As the volume ofthe spring-bag (256) decreases, more of the chemical reactor chamber(260) volume may be used for conducting the chemical reaction. Hydrogenproduced from the reaction in the chemical reaction chamber (260) may beprovided to an anode of a fuel cell apparatus such as the apparatusdescribed with reference to FIGS. 1 and 2.

Referring next to FIG. 6, another embodiment of a hydrogen generatingapparatus (354) is shown. The embodiment of FIG. 6 is similar to thatshown in FIG. 5, however, according to the embodiment of FIG. 6, thechemical reaction chamber is a flexible reaction bag (360). A spring-bag(356) may be disposed within the flexible reaction bag (360) and providepressure to any hydrogen-bearing fuel solution (such as sodiumborohydride) contained therein. As described above, the spring-bag (356)may provide pressure when it is elastically expanded as it is filledwith a hydrogen-bearing fuel solution. The spring-bag (356) may be freefloating within the flexible reaction bag (360), or may be attached tothe flexible reaction bag (360).

A fluid communication path (364) facilitates the transfer of thehydrogen-bearing chemical solution (such as aqueous sodium borohydride)from the spring-bag (356) to the flexible reaction bag (360). The fluidcommunication path (364) may be at least partially external to theflexible reaction bag (360) as shown, or the fluid communication path(364) may be entirely internal to the flexible reaction bag (360). Theflexible reaction bag (360) may contain a catalyst for increasing therate of reaction of the hydrogen-bearing fuel solution. The fluidcommunication path (364) may also include a control valve such asmicro-valve (366) to meter the hydrogen-bearing fuel solution from thespring-bag (356) to the flexible reaction bag (360). Similar to theembodiments shown in FIGS. 4 and 5, as the supply of hydrogen-bearingsolution such as aqueous sodium borohydride is transferred from thespring-bag (356) to the flexible reaction bag (360), the volume of thespring-bag (356) decreases. As the volume of the spring-bag (356)decreases, more of the flexible reaction bag (360) volume may be usedfor conducting the chemical reaction. Further, the volume of theflexible reaction bag (360) may increase as the supply ofhydrogen-bearing solution enters. The flexible reaction bag may also actas an expanding waste reservoir housing the remaining products followingthe chemical reaction to produce hydrogen gas. The embodiment of FIG. 6as described herein may be particularly lightweight as compared toconventional hydrogen generating systems.

Referring next to FIG. 7, another embodiment of a hydrogen generatingapparatus (454) for a fuel cell is shown. According to the embodiment ofFIG. 7, the hydrogen generating apparatus (454) includes a chemicalsolution reservoir embodied as a fresh solution bag (456), and achemical reaction chamber embodied as a reaction chamber bag (460). Thefresh solution bag (456) may contain a hydrogen-bearing fuel solutionsuch as aqueous sodium borohydride, and the reaction chamber bag (460)may contain a catalyst (not shown). Both the fresh solution bag (456)and the reaction chamber bag (460) may be flexibly contained by a rigidframe (457). Advantageously, the rigid frame (457) need not befluid-tight and resistant to fluid corrosion as prior hydrogengenerating systems require, which simplifies the structure of the rigidframe (457) and enables the use of less expensive and lighter-weightmaterials. The reaction chamber bag (460) may prevent thehydrogen-bearing solution from collecting in corners and crevices thatmay be present inside a rigid shell reaction chamber such as thatembodied in FIGS. 3 and 4.

The fresh solution bag (456) and the reaction chamber bag (460) may beseparated from one another by a pressure plate (465). The pressure plate(465) may be a pressure producing member adjacent to and abutting thefresh solution bag (456) and/or the reaction chamber bag (460). One ormore biasing members, for example first and second coiled springs (467and 469), provide a force on the pressure plate (465). The forceprovided by the first and second coiled springs (467 and 469) istransferred to the fresh solution bag (456) via the pressure plate (465)to increase the pressure on the hydrogen-bearing solution in thesolution bag (456).

A fluid communication path (464) facilitates the transfer of thehydrogen-bearing chemical solution (such as aqueous sodium borohydride)from the fresh-solution bag (456) to the reaction chamber bag (460). Thefluid communication path (464) may be at least partially external to therigid frame (457) as shown, or the fluid communication path (464) may beentirely internal to the rigid frame (457). The reaction chamber bag(460) may contain a catalyst for increasing the rate of reaction of thehydrogen-bearing fuel solution. The fluid communication path (464) mayalso include a control valve such as a micro-valve (466) to meter thehydrogen-bearing fuel solution from the fresh solution bag (456) to thereaction chamber bag (460). As the supply of hydrogen-bearing solutionsuch as aqueous sodium borohydride is transferred from the freshsolution bag (456) to the reaction chamber bag (460), the pressure plate(465) displaces toward the fresh solution bag (456) and will decreasethe volume of the fresh solution bag (456) and increase the reactionchamber bag (460). The reaction chamber bag (460) may therefore also betermed a waste reservoir for collection products after the reaction toproduce hydrogen has completed. Alternatively, an additional wastereservoir similar or identical to the reaction chamber bag (460) may beincluded internal or external to the rigid frame (457) for collectingwaste products. Hydrogen produced in the reaction chamber bag (460) maybe provided to an anode of a fuel cell apparatus such as the apparatusdescribed with reference to FIGS. 1 and 2.

Referring next to FIG. 8, another embodiment of a hydrogen generatingapparatus (554) is shown. The hydrogen generating apparatus (554) isshown in a piston-cylinder arrangement. A piston (555) disposed in acylinder (557) divides the cylinder (557) into a chemical solutionreservoir portion (556) and a reaction chamber portion (560). A spring(558) may be disposed between the piston (555) and a wall (559) of thecylinder (557) to provide pressure on the chemical solution reservoirportion (556) of the cylinder (557) and facilitate the movement of achemical solution such as sodium borohydride from the chemical solutionreservoir portion (556) of the cylinder (557) to the reaction chamberportion (560) of the cylinder (557). The spring (558) may also move thepiston toward the chemical solution reservoir portion (556) of thecylinder (557). The embodiment of FIG. 8 is particularly space-efficientas it does not use bags which may not completely utilize all spaceinside of a rigid shell. In addition, the embodiment of FIG. 8 reducesor eliminates any waste solution in the chemical solution reservoirportion (556) of the cylinder (557) that may otherwise be trapped incorners or folds of a bag.

A fluid communication path (564) facilitates the transfer of thechemical solution (such as aqueous sodium borohydride) from the chemicalsolution reservoir portion (556) of the cylinder (557) to the reactionchamber portion (560) of the cylinder (557). The fluid communicationpath (564) may be at least partially external to the cylinder (557) asshown. Alternatively, the fluid communication path (564) may be disposedin the piston (555). The reaction chamber portion (560) of the cylinder(557) may contain a catalyst for increasing the rate of reaction of thechemical solution. The fluid communication path (564) may also include acontrol valve such as a micro-valve (566) to meter the chemical solutionfrom the chemical solution reservoir portion (556) of the cylinder (557)to the reaction chamber portion (560). As the supply of aqueous sodiumborohydride is transferred from the chemical solution reservoir portion(556) of the cylinder (557) to the reaction chamber portion (560), thespring (558) moves the piston (555) toward the chemical solutionreservoir portion (556) and the volume of the chemical solutionreservoir portion (556) decreases. As the volume of the chemicalsolution reservoir portion (556) of the cylinder (557) decreases, moreof the cylinder (557) volume may be used for the reaction chamberportion (560). Hydrogen produced in the reaction chamber portion (560)of the cylinder (557) may be provided to an anode of a fuel cellapparatus such as the apparatus described with reference to FIGS. 1 and2.

It will be appreciated by those of skill in the art having the benefitof this disclosure that the embodiments described advantageously providefor metering of a hydrogen-bearing fuel source to a chemical reactionchamber in an orientation-independent manner. That is, the hydrogengenerating apparatus (54, 154, etc.) may be operable in any orientationbecause the pressure producing members provide a pressure differentialbetween the chemical solution reservoirs (56, 156, etc.) and thechemical reaction chambers (60, 160, etc.) in any orientation. This maybe especially important for fuel cell applications in portableelectronics—which are often moved and reoriented in many different ways.In addition, some embodiments of the present invention may use only asingle control valve (66, 166, etc.), reducing the occurrence offailures present in prior hydrogen generating systems that require pumpsand multiple control valves. Each of the embodiments shown in FIGS. 3–8may also be implemented in hydrogen generating cartridges that areindependent and separate from—but may be coupled to—a fuel cellapparatus.

Each of the embodiments described above preferably include a controlvalve to meter the transfer of a chemical solution, such as sodiumborohydride, from a chemical reservoir to a reaction chamber. Control ofthe hydrogen generation is facilitated by the control valve (such as themicro-valves described above). Referring next to FIG. 9, a diagram of acontrol scheme for the hydrogen generating apparatus according to oneembodiment of the present invention is shown. The inputs to the controlscheme may include, but are not limited to, user settings (700),configuration settings (702), fuel cell stack voltage (704), reservoir,hydrogen gas, and/or reactor pressure (706), fuel cell current (708),and fuel cell power (710).

The user settings (700) may include switches, buttons, and the like thata user may operate to control the state of the control valve directly.The configuration settings (702) may include an initialization routineto initialize the control scheme and set operating parameters. It willbe appreciated that one or more of the inputs (700–710) may be fed intoa control algorithm (712) to control the hydrogen generating apparatus.The control algorithm may include all the necessary programming andelectronics to receive input, analyze the input received, and provideappropriate and corresponding control signals to the control valve. Thecontrol algorithm may thus include a digital electronic controller, ananalog electronic controller, or a mechanical controller. The controlalgorithm may use any or all of the inputs (700–710) to issue commandstate information (output). The command state information may includethe current valve state (714) indicative of valve position(open/closed), and/or timing information (716) indicating valveoperating frequency. Depending on the control algorithm output, thecontrol valve may be opened or closed (718) to control the flow ofchemical solution from a reservoir to a reaction chamber, and thus therate of hydrogen production.

One example of a control algorithm that may be used as part of thecontrol scheme is shown in FIG. 10, however, it will be understood thatmany other and/or additional control algorithms may be used by those ofskill in the art having the benefit of this disclosure to meetindividual needs and that FIG. 10 is merely an example. For example aproduction controller could vary the pulse width and/or the aperturesize of a control valve in addition to the changing the frequency thevalve is opened. Furthermore, a battery, capacitor, or other energystorage device could be added to the system (as shown in FIG. 2) tode-couple the fuel cell from the load to keep the fuel cell operating atits most efficient rate.

According to the exemplary embodiment of FIG. 10, the control algorithmmay initialize (800) and wait for a timer to expire (801), then checkfor fuel cell stack voltage (802). In some embodiments, however, thereis no timer. If the fuel cell stack voltage is above a predetermined“High” limit (804), the control algorithm progresses to set a valvetimer to a “High” delay frequency (806) and the stack voltage iscontinually or, in embodiments with a timer, periodically checked again(802) after expiration of a timer (801). If the fuel cell stack voltageis not above the predetermined “High” limit (804), the control valve ispulsed once (808) and the algorithm checks for fuel cell stack voltagebelow a “Medium” limit (810). If the fuel cell stack voltage is notbelow the “Medium” limit (810), the valve timer is set to a “Medium”delay frequency (812) and the stack voltage is continually or, inembodiments with a timer, periodically checked again (802) after theexpiration of a timer (801). If, however, the fuel cell stack voltage isbelow the “Medium” limit, the valve timer is set to a “Low” delayfrequency (814) and the stack voltage is continually or periodicallychecked again (802).

The preceding description has been presented only to illustrate anddescribe the invention. It is not intended to be exhaustive or to limitthe invention to any precise form disclosed. Many modifications andvariations are possible in light of the above teaching.

The embodiments shown were chosen and described in order to best explainthe principles of the invention and its practical application. Thepreceding description is intended to enable others skilled in the art tobest utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the followingclaims.

1. A hydrogen generating apparatus comprising: a chemical reactionchamber; a chemical solution reservoir; and a biasing member forproviding pressure to move a chemical solution from said chemicalsolution reservoir to said chemical reaction chamber where hydrogen isproduced from said chemical solution; wherein said chemical solutionreservoir is contained by said chemical reaction chamber such that areaction conducted in said reaction chamber applies additional pressureto said chemical solution reservoir and chemical solution.
 2. Theapparatus of claim 1, wherein said chemical solution reservoir comprisesa flexible bag.
 3. The apparatus of claim 2, wherein said biasing membercomprises a spring configured to apply pressure to said flexible bag ofsaid chemical solution reservoir.
 4. The apparatus of claim 3, furthercomprising a plate disposed between said spring and said flexible bag.5. The apparatus of claim 2, where said flexible bag of said chemicalsolution reservoir comprises a spring-bag as said biasing member.
 6. Theapparatus of claim 5, wherein said spring-bag comprises an elastomer. 7.The apparatus of claim 1, wherein said chemical reaction chambercomprises a flexible bag.
 8. A hydrogen generating apparatus comprising:a chemical reaction chamber; a chemical solution reservoir; and a springfor providing pressure to move a chemical solution from said chemicalsolution reservoir to said chemical reaction chamber where hydrogen isproduced from said chemical solution; wherein said chemical solutionreservoir comprises a flexible bag.
 9. The apparatus of claim 8, whereinsaid chemical reaction chamber comprises a flexible bag.
 10. Theapparatus of claim 8, wherein said spring is configured to applypressure to said flexible bag.
 11. The apparatus of claim 10, furthercomprising a plate disposed between said spring and said flexible bag.12. The apparatus of claim 8, where said flexible bag and springcomprise a spring-bag, said spring applying pressure to opposite sidesof said flexible bag to move said chemical solution.
 13. The apparatusof claim 12, wherein said spring-bag comprises an elastomer.
 14. Ahydrogen generating apparatus comprising: a chemical reaction chamber; achemical solution reservoir; a spring for providing pressure to move achemical solution from said chemical solution reservoir to said chemicalreaction chamber where hydrogen is produced from said chemical solution;and a control valve disposed in a fluid communication path between saidchemical solution reservoir and said reaction chamber.
 15. The apparatusof claim 14, wherein said control valve is a micro-valve operable atvariable frequencies, pulse widths, or aperture sizes by a controller.16. The apparatus of claim 15, wherein said controller monitors a stackvoltage of a fuel cell and adjusts one or more of said frequency, pulsewidth, or aperture size of said micro-valve in response to changes insaid stack voltage.
 17. The apparatus of claim 16, wherein saidcontroller increases said frequency, pulse width, or aperture size ofsaid micro-valve in response to a monitored stack voltage above apredetermined threshold.
 18. The apparatus of claim 16, wherein saidcontroller decreases said frequency, pulse width, or aperture size ofsaid micro-valve in response to a monitored stack voltage below apredetermined threshold.
 19. The apparatus of claim 15, wherein saidcontroller monitors one or more of user settings, configurationsettings, hydrogen gas pressure, fuel cell current, and fuel cell power;and adjusts one or more of said frequency, pulse width, or aperture sizeof said micro-valve in response to monitored changes.
 20. The apparatusof claim 15, further comprising a battery to power said controller. 21.The apparatus of claim 14, further comprising a check valve disposed insaid communication path between said control valve and said chemicalreaction chamber.
 22. A hydrogen generating apparatus comprising: achemical reaction chamber; a chemical solution reservoir; and a springfor providing pressure to move a chemical solution from said chemicalsolution reservoir to said chemical reaction chamber where hydrogen isproduced from said chemical solution; wherein said chemical reactionchamber and said chemical solution reservoir comprise respectiveportions of a cylinder separated by a piston.
 23. The apparatus of claim22, wherein said spring is configured for operating said piston toprovide pressure to move said chemical solution from said chemicalsolution reservoir to said chemical reaction chamber.
 24. A hydrogengenerating apparatus comprising: a chemical reaction chamber; a chemicalsolution reservoir; and a biasing member for providing pressure to movea chemical solution from said chemical solution reservoir to saidchemical reaction chamber where hydrogen is produced from said chemicalsolution; wherein said chemical solution reservoir is contained by saidchemical reaction chamber such that, as a reaction is conducted in saidreaction chamber, a volume of said reservoir decreases while a volume ofsaid reaction chamber increases.
 25. The apparatus of claim 24, whereinsaid increase in volume of said reaction chamber is used to house wasteproducts from said reaction.